U.S. Pat. No. 5,232,458 to Long-Hsiung Chen disclosed a safety syringe including a hollow needle having a needle head portion formed on a rear portion of the needle, and a plunger slidably held in the syringe having a biasing socket recessed in a front portion of the plunger engageable with the needle head portion for biasing the needle obliquely within the syringe when retracting the plunger and the needle into the syringe to prevent an outward protruding of the retracted needle for preventing its injury or infectious contamination to the surroundings.
However, such a conventional safety syringe may have the following drawbacks:
1. When mounting the needle device (2) on the syringe (1), the needle device (2) should be inserted through the plug (13) in the sleeve portion (12) of the syringe (1) to thereby cause inconvenience. PA1 2. It can not be replaced with needles of different sizes outside the syringe. PA1 3. A plug (13) is embedded in a front portion within the syringe cylinder (11) to possibly increase the assembly difficulty and production cost.
The present inventor has found the drawbacks of the conventional safety syringe and invented the present safety syringe with externally connectable needle.